Evasion of host cell defense mechanisms by pathogenic bacteria.

From an immunological viewpoint, invasion of pathogenic bacteria into a susceptible host poses a potential life-threatening situation and thus has to be met with all weapons that are available. A crucial component of host defense mechanisms is the macrophage. The scavenger activity of this cell ensures the uptake and destruction of bacteria in phagolysosomes, on the one hand, and activation of the adaptive component of the immune system through presentation of bacterial antigens, on the other hand. From the bacterial perspective, entry into a phagolysosome is usually fatal and many pathogens have developed strategies that circumvent the destructive environment of this organelle. Such evasion strategies often exploit normal host cell function. Understanding these survival strategies will deepen our insight of the pathogenesis of infection as well as host cell biology.